I have Koni adjustables (yellow) and like them alot.
But I really wanted these, since they are suppose to be one of the best, if not the best on the market for the GTO. I had a set of the IAS on my truck and was blown away at how they handled changing road surfaces and conditions. Too bad they were outta my price range at the time of my purchase.
NOTE: The following is a copy and paste from my email dialogue with John. I can't find the other email (may have deleted it), but I believe that he mentioned that with his solution you can install 265 tires up front:
Both front and rear are progressive rate coils, or we do have a linear rate set available for street work, rates are as follows.
Front - Static 65N/mm to 105N/mm (370 lb/in to 600lb/in)
Rear - Static 65N/mm to 90N/mm to 110N/mm (370lb/in to 515lb/in to 630lb/in)
Front - Static 50N/mm (286lb/in)
Rear - Statitc 65N/mm (370lb/in)
This is totally dependant on the type of tyre and what you are doing with the car, eg driving around town or serious track work. Alignment will vary from neg 1.5 as you have and up to neg 2.75 for track work. You have to measure the tyre temp. to find out what the best settings are for race work.
With this kit you can put your standard swaybar back on, the heavier bars cause understeer on the front and oversteer on the rear when you use them with the heavy spring rates. It is the heavy spring rate that gives you the precise control, not sway bars.
The kit we make was developed for racing the GTO (Monaro in Australia) in tarmac rally events. It was built for a very famous touring car driver in Aust. by the name of Peter Brock. We use Edelbrock shocks for both front and rear, with the front you get a complete replacement front strut that comes with a 50mm (2") insert and a 60mm (2.36") strut housing. It is not a part that you have to cut up your original strut then fit another piece into it to act as the shock as is with the Koni insert.
Another thing that has been changed in our design is the front coil spring, there is a very good reason for this. If you use the original front strut housing and install a lowered front coil that drops the front to a ride height of 335mm, that is about 25mm lower than the GTO you only have 15mm of front suspension travel using the original front strut housing.
Koni say they have a shortened front insert that gives you an extra 20mm of travel, that is correct, BUT using the original, or an after market front coil design does not allow you to us the extra 20mm that the Koni and Bilstein insert provides. The front suspension bottoms out on the coil spring when the ride height goes down to about 320mm, so you end up with 15mm of useable travel, this is not enough.
Our new design coil is 20mm shorter than the original coil when it is fully compressed and at a ride height of 335mm measured from the centre of the wheel to the edge of the mudguard you have the same travel as the original GTO height front suspension, this being 50mm. It also allows you to fit wheels up to 22" Dia. because the lower coil seat is higher up the housing than the original seat.
Due to the fact that we use the Edelbrock IAS valve system the ride quality is very good, it is very sporty but not harsh. You can also put the car on the track or into a road race and get extremly good performance. Peter Brock was beating 4WD Turbo Porsche race cars in the wet with this suspension installed into his Monaro (GTO)
The shocks are covered by the Edelbrock warranty and the price is AUD$3403.00 for the complete kit.
I understand that these 2 Monaros (GTOs) have this suspension.
Short list of the cars that were passed as if the 2 of them were street racing on the freeway: